Hi,
On 11/10/06, Pavan Deolasee <[EMAIL PROTECTED]> wrote:
On 11/10/06, Tom Lane <[EMAIL PROTECTED]> wrote:
"Pavan Deolasee" <
[EMAIL PROTECTED]> writes:> On 11/10/06, Tom Lane <[EMAIL PROTECTED]> wrote:> (2) Isn't this full of race conditions?
> I agree, there could be race conditions. But
> > 1. It doubles the IO (original page + hot page), if the new row
would
> > have fit into the original page.
>
> That's an awfully big IF there. Even if you use a fillfactor
> of 50% in which case you're paying a 100% performance penalty
I don't see where the 50% come from ? That's only
On 11/10/06, Tom Lane <[EMAIL PROTECTED]> wrote:
"Pavan Deolasee" <[EMAIL PROTECTED]> writes:> On 11/10/06, Tom Lane <[EMAIL PROTECTED]> wrote:> (2) Isn't this full of race conditions?
> I agree, there could be race conditions. But IMO we can handle those.Doubtless you can prevent races by introd
> > I think the vision is that the overflow table would never be very
> > large because it can be vacuumed very aggressively. It has only
tuples
> > that are busy and will need vacuuming as soon as a transaction ends.
> > Unlike the main table which is mostly tuples that don't need
> > vacuumi
Hi,I think the vision is that the overflow table would never be very large
because it can be vacuumed very aggressively. It has only tuples that are busyand will need vacuuming as soon as a transaction ends. Unlike the main tablewhich is mostly tuples that don't need vacuuming.
Thats right. vacuum
"Zeugswetter Andreas ADI SD" <[EMAIL PROTECTED]> writes:
> 1. It doubles the IO (original page + hot page), if the new row would
> have fit into the original page.
That's an awfully big IF there. Even if you use a fillfactor of 50% in which
case you're paying a 100% performance penalty *al
On 11/10/06, Heikki Linnakangas <[EMAIL PROTECTED]> wrote:
Tom Lane wrote:> (Actually, the assumption that you can throw an additional back-pointer> into overflow tuple headers is the worst feature of this proposal in> that regard --- it's really not that easy to support multiple header
> formats.)
> > As more UPDATEs take place these tuple chains would grow, making
> > locating the latest tuple take progressively longer.
> More generally, do we need an overflow table at all, rather
> than having these overflow tuples living in the same file as
> the root tuples? As long as there's a b
Tom Lane wrote:
"Pavan Deolasee" <[EMAIL PROTECTED]> writes:
Yes. The last bit in the t_infomask is used up to mark presence of overflow
tuple header. But I believe there are few more bits that can be reused.
There are three bits available in the t_ctid field as well (since ip_posid
needs maximu
On 11/10/06, Tom Lane <[EMAIL PROTECTED]
> wrote:
"Pavan Deolasee" <[EMAIL PROTECTED]> writes:> Yes. The last bit in the t_infomask is used up to mark presence of overflow
> tuple header. But I believe there are few more bits that can be reused.
> There are three bits available in the t_ctid field
"Pavan Deolasee" <[EMAIL PROTECTED]> writes:
> On 11/10/06, Tom Lane <[EMAIL PROTECTED]> wrote:
> (2) Isn't this full of race conditions?
> I agree, there could be race conditions. But IMO we can handle those.
Doubtless you can prevent races by introducing a bunch of additional
locking. The qu
On 11/10/06, Tom Lane <[EMAIL PROTECTED]> wrote:
"Pavan Deolasee" <[EMAIL PROTECTED]> writes:> On 11/10/06, Josh Berkus <
josh@agliodbs.com> wrote:
>> I believe that's the "unsolved technical issue" in the prototype, unless>> Pavan has solved it in the last two weeks. Pavan?>>> When an overflow
"Pavan Deolasee" <[EMAIL PROTECTED]> writes:
> On 11/10/06, Josh Berkus wrote:
>> I believe that's the "unsolved technical issue" in the prototype, unless
>> Pavan has solved it in the last two weeks. Pavan?
>>
> When an overflow tuple is copied back to the main heap, the overflow tuple
> is
>
On 11/10/06, Josh Berkus wrote:
Tom,> Actually, you omitted to mention the locking aspects of moving tuples> around --- exactly how are you going to make that work without breaking> concurrent scans?I believe that's the "unsolved technical issue" in the prototype, unless
Pavan h
Tom,
> Actually, you omitted to mention the locking aspects of moving tuples
> around --- exactly how are you going to make that work without breaking
> concurrent scans?
I believe that's the "unsolved technical issue" in the prototype, unless
Pavan has solved it in the last two weeks. Pavan?
"Simon Riggs" <[EMAIL PROTECTED]> writes:
> As more UPDATEs take place these tuple chains would grow, making
> locating the latest tuple take progressively longer.
This is the part that bothers me --- particularly the random-access
nature of the search. I wonder whether you couldn't do something
Simon,
> If we perform an update that meets the HOT criteria then we put the
> new version into the overflow relation; we describe this as a HOT
> UPDATE. If we perform an update that does not meet the criteria, then we
> carry on with the existing/old MVCC behaviour; we describe this as a
> non-H
Nice idea, just one question:
On Thu, Nov 09, 2006 at 05:13:16PM +, Simon Riggs wrote:
> Behavioural Characteristics
> ---
>
> With HOT, it is easily possible that the chain of prior versions spans
> many blocks. The chain always starts with the block of the root tuple
Design Overview of HOT Updates
--
The objective is to increase the speed of the UPDATE case, while
minimizing the overall negative effects of the UPDATE. We refer to the
general requirement as *Frequent Update Optimization*, though this
design proposal is for Heap Overf
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